The present invention relates to an optical observation device for observing an eye according to the preamble of patent claim 1. In particular, the present invention relates to an optical observation device, by means of which the anterior eye and the retina can be alternately observed, in particular, stereoscopically.
For this purpose, different solutions are already known in the prior art. For example, an alternating observation can be achieved by means of a stereoscopic operating microscope with a fundus imaging system, as is described, for example, in the German Utility Model G 94 15 219.5 U1. The known fundus imaging system comprises an ophthalmoscopic loupe and a reducing lens, which are positioned underneath the principal objective of the operating microscope, in order to make possible an imaging of the fundus, and thus the retina of the eye. An intermediate image of the retina is produced by means of the ophthalmoscopic loupe and this image is observed with the operating microscope. The reducing lens shortens the working distance and thus makes possible the imaging of the intermediate image in the intermediate image plane in front of the eyepiece of the operating microscope. With the help of a positioning device, the ophthalmoscopic loupe can be positioned in such a way that the fundus of the eye is sharply imaged.
This image, which is observed in this way, however, is vertically and laterally reversed as well as pseudo-stereoscopic, i.e., front and back are reversed in depth perception. For this reason, a correcting of the image and a pupil reversal are necessary, in the known solution, in order to be able to operate microsurgically.
Different fundus imaging systems for operating microscopes with image correction and pupil reversal are described in the publications DE 101 40 402 A1, DE 41 14 646 C2, or DE 35 39 009 A1.
In ophthalmic surgery, operating microscopes are frequently used for interventions in the anterior eye and for interventions on the retina. The cataract operation is a frequent intervention in the anterior eye, whereas so-called epiretinal membrane peeling represents a typical intervention on the retina.
Direct contact glasses, which are placed on the cornea of the eye, are also used very often in ophthalmic surgery as an alternative to ophthalmoscopic loupe/reducing lens systems. In the case of direct contact glasses, an intermediate image of the retina is not produced in the imaging beam path of the operating microscope, but rather the fundus is imaged directly with the operating microscope. In this case, an image correction and a pupil reversal are not necessary.
The older publication EP 1 889 567 A2 describes an operating microscope with a fundus imaging system in which the illumination is guided past the ophthalmoscopic loupe in order to avoid disruptive reflections.
An operating microscope is described in DE 103 02 401 A1, which is constructed similarly to the one in the above-named G 94 15 219 U1. The operating microscope has a microscope means. In addition, a means for visualizing is provided, which serves for diagnosing the retina. The visualizing means provides a camera for recording images of the retina. In addition, the operating microscope provides an attachment means with attachment lenses, which—with the above-described disadvantages—can be introduced into the optical beam path of the microscope means. The difference relative to G 94 15 219 U1 consists only in that the image of the retina is no longer presented in the optical beam path; rather, the image in the operating microscope is decoupled via a beam splitter and is introduced into a camera.
In the case of solutions known in the prior art, an alternating between the anterior and posterior regions of the eye is produced either by swinging in an ophthalmoscopic loupe/reducing lens combination or by placing a direct contact glass on the cornea and appropriate focusing of the operating microscope.
The named prior art, however, has a number of disadvantages, for example, an image correction and a pupil reversal are necessary when an ophthalmoscopic loupe and reducing lens are used. The image correction and pupil reversal can be accomplished in known systems only with a great deal of complexity, such as is clarified in the publications DE 101 40 402 A1, DE 41 14 646 C2 or DE 35 39 009 A1.
In addition, only a moderate imaging quality is achieved when an ophthalmoscopic loupe is used. The reason for this is that the ophthalmoscopic loupe must be autoclavable and for this reason comprises a single lens—and often, in fact, this does not have an antireflection coating.
Also, an ophthalmoscopic loupe can be positioned only with a great deal of effort and imprecisely for the surgeon, since it is joined only very loosely with the operating microscope for safety reasons and thus can be very easily displaced laterally off-center. Another difficulty with the positioning consists of the fact that the distance of the ophthalmoscopic loupe from the eye is not defined and vignetting can occur at too great a distance.
Reducing lenses, ophthalmoscopic loupes and their mounts usually need to be autoclavable. This requirement for sterilization is complicated and makes progress difficult for the surgical operation.
The conventional illumination of an operating microscope for ophthalmic surgery is designed either as oblique lighting or as coaxial lighting with oblique lighting. When an ophthalmoscopic loupe is used, in all cases, there are reflections of the illumination at the interfaces of the ophthalmoscopic loupe.